1. Technical Field
The present invention relates to an electro-optical device, an electronic apparatus on which the electro-optical device is mounted, and a method for manufacturing the electro-optical device.
2. Related Art
As an electro-optical device, for example, an active drive type liquid crystal device which is used as an optical modulation measure (light bulb) of a liquid crystal projector, is used. In a pixel of the liquid crystal device, a storage capacitor is formed for retaining an image signal which is written into a pixel electrode, and potential retention properties of the image signal in the pixel electrode is enhanced.
For example, an electro-optical device (liquid crystal device) which is described in JP-A-2013-25069, has a storage capacitor where a first electrode, a dielectric layer, and a second electrode are stacked in sequence. The first electrode is formed over a plurality of pixels, and a common potential is supplied thereto. That is, the first electrode is a capacitance line to which the common potential is supplied. The first electrode has a two-layered structure where aluminum and a titanium nitride are stacked in sequence, and lowering of resistance is achieved by the aluminum which is positioned on the lower layer side, and a change of the potential which is supplied to the first electrode is suppressed. The second electrode is formed into an island shape per pixel, and the potential which is supplied to the pixel electrode is supplied thereto.
Furthermore, between the first electrode and the dielectric layer, an insulating film (etching stopper) which protects the first electrode is formed so that the first electrode is not affected at the time of etching the dielectric layer and the second electrode. In the insulating film, an opening which exposes a surface (portion where the titanium nitride is positioned) of the first electrode is formed. The dielectric layer and the second electrode are stacked in sequence on the surface of the first electrode which is exposed by the opening of the insulating film, and thereby, the above-described storage capacitor is formed. Hence, a capacitance value of the storage capacitor depends on an opening area (exposed area of the surface of the first electrode) of the insulating film.
The opening of the insulating film is formed by performing a dry etching treatment of the insulating film. If the insulating film is dry-etched, a reaction product (deposition material) is deposited on the etched face (surface of the first electrode which is exposed by the opening). Since the reaction product increases the resistance of the surface of the first electrode, there is a need of removing the reaction product by being immersed in a drug solution containing hydrofluoric acid after the dry etching of the insulating film.
In the liquid crystal device of the light bulb purpose, there is the need of making capacitance enlargement of the storage capacitor in order to obtain an image of high quality while achieving refinement (densification) of the pixel. Furthermore, if the pixel is refined (densified), since the capacitance line (first electrode) of the storage capacitor becomes thin, there is the need of forming the capacitance line (first electrode) by aluminum of a low resistance material, and of suppressing the increase of the resistance (time constant) of the capacitance line (first electrode). However, in the electro-optical device which is described in JP-A-2013-25069, when the capacitance line (first electrode) is formed by the aluminum of the low resistance material, there is a problem that the capacitance enlargement of the storage capacitor is unlikely to be achieved.
Specifically, in the aluminum of the low resistance material, a tolerance with respect to the drug solution containing hydrofluoric acid is weak. In order to make the capacitance enlargement of the storage capacitor, if the opening area of the insulating film is increased, a portion where the aluminum of the first electrode is positioned may be exposed. If the portion where the aluminum of the first electrode is positioned is exposed, a failure that the aluminum is affected (corroded) is generated, by the treatment (immersing) of the drug solution containing hydrofluoric acid for removing the reaction product. Hence, there is the problem that the opening area of the insulating film becomes large, and the capacitance enlargement of the storage capacitor is unlikely to be achieved.